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material design stress Question
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Posted by: Albert ®

12/16/2004, 04:58:09

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For ductile material, I have been using material shear yield stress = 0.58 x material tension yield stress.....and also bearing yield stress = 1.6 material tensin stress.  I prepared the design calculation and the third party reviewer asked how I support the above figure.

Does anyone know of the source reference?  One book refer the bearing stress back to ASME code on rivet design.   







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Re: material design stress
Re: material design stress -- Albert Post Reply Top of thread Forum
Posted by: crbeebe ®

01/15/2005, 22:56:10

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The 0.58 factor can be derived from the Von-Mises criterion. Von-Mises criterion is a failure theory that is based on the 3D stress state, and yields a scalar value for stress—the “von Mises stress”. Per the theory, failure occurs when the VM stress exceeds the tensile strength of the material.

For your example, let’s assume a pure shear state in the material in a single plane. The VM equation for such a stress state reduces to

VM stress = sqrt ( 1/2 * (6* tau^2 )) = sqrt (3) * tau

where “tau” is shear stress.

Since the shear state is assumed to be pure shear stress, failure will occur when tau reaches the shear strength (“tau-yield”) of the material. And, since failure occurs when the VM stress exceeds the tensile strength of the material,

VM stress = tensile strength = sqrt (3) * tau-yield
So, tau-yield = tensile strength / sqrt (3) = 0.577 * tensile strength

I don’t have a source for the 1.6 bearing stress factor.







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Re: material design stress Smile
Re: Re: material design stress -- crbeebe Post Reply Top of thread Forum
Posted by: Albert ®

01/16/2005, 20:20:30

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Crbeebe....thanks for the help.






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